houdini_attributes_and_groups

////////////////////////////////
// houdini attributes and groups
////////////////////////////////

///////////////////////
// attributes as groups
// credit here: http://www.tokeru.com/cgwiki/?title=Houdini
// the below can be entered as expressions in any goup field
// not spaces, no semi colon, must be conditional, must be cast using "s, i, f", etc
// floats don't need casting

@P.y<0
s@side=="inside"

///////////////////////
// groups as attributes
// credit here: http://www.tokeru.com/cgwiki/?title=Houdini
// a group can also be treated as an attribute, just add "@group_" to the group name
// works well in atribute wrangles

if (!i@group_mygroup) {
    // do thing
}

// also works to create groups
if (@ptnum>chi('threshold')) {
 i@group_mygroup=1;
}